Device for in-vessel treatment

ABSTRACT

The present invention relates to a device for treatment of material in a vessel, particularly for dispersion or homogenization of liquids, or for suspension of solids in liquids. The device comprises a treatment element that is rotationally mounted in the vessel and that has an essentially tubular configuration comprising two ends. The jacket of the treatment element has a plurality of cuts formed with sharp edges, which may be drawn through the material in the vessel as the treatment element rotates, in order to transfer shearing forces to said material. The shearing forces produce the desired treatment in the vessel.

FIELD OF THE INVENTION

The present invention relates to a device for in-vessel treatment ofmaterial, particularly for dispersion or homogenisation of liquids, orfor suspension of solids in liquids, of the kind comprising a treatmentelement that is rotationally mounted in the vessel.

BACKGROUND OF THE INVENTION

In mixing liquids in a vessel, a rotary stirrer usually is used, forexample a stirrer having radially outwardly directed vanes. A stirrer ofthis kind is adapted to transfer energy to the liquid in two ways.Firstly, the liquid is set in motion as the vanes are drawn throughliquid, whereby a laminar flow is created. Secondly, the liquid isaffected by shearing forces at the vane edges, which causes turbulence.

In some situations, the mixing process is dependent on the presence ofextremely strong shearing forces. This is true in the dispersion orhomogenisation of liquids that do not spontaneously form a solution (forexample oil in water) and in suspending powdered solids in a liquid(such as flour in water). The considerable shearing forces are requiredto break up for example drops of oil or lumps of flour into atomisedparticles through “whipping”. When conventional stirrers are used, avery large moment of force is required to deliver shearing forces ofthis magnitude.

U.S. Pat. No. A 5,205,647 suggests a solution to the above problem. Themixing apparatus described therein has a cylindrical casing, in which isattached a sleeve formed with oblong slots, and a cylinder rotationallymounted in the casing. The cylinder is formed With through-botesextending in the cylinder material in parallel with the cylinder axis,and apertures extending between the bores and the exterior of thecylinder. The mixing apparatus operates by introducing liquids throughtwo inlets while the cylinder is rotating. The liquids are introducedinto the bores and thereafter are passed through the apertures to theexterior of the cylinder and thereafter through the oblong slots in thecasing to finally exit through an outlet in the casing. On their route,the liquids are exposed to shearing forces.

In accordance with another prior-art apparatus two concentric cylindersare arranged to rotate relative to one another, for example inside atank. The cylinders are formed with through-outlets and are disposedsufficiently closed to one another to ensure that a scissors-like forceis produced, when they rotate relative to one another. Liquid subjectedto this scissors-like force is affected by considerable shearing forces.

Several disadvantages are connected with the prior-art techniquedescribed above. The apparatuses comprise several components, which aremovable relative to one another and between which the spacing bynecessity must be extremely narrow if the large shearing forces are tobe produced. The manufacturing tolerances as well as the assembly andmounting tolerances with respect to the discrete components thereforeare extremely small.

Should some components happen to come into contact with one anotherduring the rotation, there is a risk that particles may separate fromthe contacting components and pollute the liquid to be mixed therewith.In case of heavy contact, there is also a risk that the apparatus may beseriously damaged.

Considering the large number of components that must be produced,mounted and made to co-operate with a high degree of precision in orderto produce the desired effect, the apparatuses become expensive tomanufacture and to maintain.

In addition, the narrow spaces formed between the various components aredifficult to clean. Particles and viscous liquid may get trapped inthese narrow spaces and form obstructions, which impairs the functionalability of the apparatus

SUMMARY OF THE INVENTION

One object of the present invention is to provide a device for in-vesseltreatment, which is capable of efficiently mixing, dispersing and/orhomogenising liquids under the conditions outlined above withoutrequiring a large moment of force. By “liquid” as used herein should beunderstood all fluid substances (media?) as also liquids/fluidscontaining solid particles.

A second object of the invention is to provide an easy-to-cleanapparatus for in-vessel treatment.

A third object of the invention is to provide an apparatus for in-vesseltreatment that does not require a large number of components that aremovable relative to one another.

A fourth object of the invention is to provide an apparatus forin-vessel treatment that is inexpensive and simple to manufacture.

These and other objects are achieved according to the invention by meansof an apparatus of the kind define in the introduction hereto and whichis characterised in that the treatment element essentially is of tubularconfiguration and is formed with a plurality of cuts formed with sharpedges which are drawn through the material in the vessel as thetreatment element rotates, in order to transfer shearing forces to saidmaterial.

Upon rotation of the treatment element in liquid, the sharp edgesthereon generate a resistance force, as they move through the liquid.Because of the sharpness of the edges, the motion of the latter affectsthe liquid by means of shearing forces, and the moment of force requiredto rotate the treatment element consequently is transferred to a veryhigh extent to the liquid in the form of shearing forces.

The treatment element preferably is cylindrical and is mounted forrotation about its centre axis. Resistance against the rotary motionthen is generated almost exclusively from the sharp edges, since therest of the treatment element is configured as a rotationallysymmetrical element.

In addition, the treatment element can be configured as a multi-pieceelement. For example, it may be designed in the form of several cylindersectors, or in the form of several concentric cylinders. In addition oneor both ends of the treatment element may be formed with inwardlydirected flanges. Alternatively, the treatment element may be formedwith a barrel-shaped contour configuration, presenting smaller radii atits ends than in its in-between parts. Owing to this configuration, itbecomes more difficult for liquid that is forced against the jacket ofthe treatment element to flow axially along the jacket of the treatmentelement and across the edge of the latter, and in consequence thereofthe liquid is instead forced to pass through the cuts.

In addition, the cuts may be formed with shovel means the mouths ofwhich are orientated in the direction of rotation of the treatmentelement, which mouths are formed with sharp edges. Preferably, theshovel means are formed on the inner face of the treatment element. Inthe course of rotation of the element, the shovel means urge liquid topass from the inner face of the treatment element, through the cuts tothe external face of the treatment element. In addition, the shovelmeans contribute to setting the liquid in a rotary motion, whereby thecentripetal force will convey liquid radially outwards, towards andthrough the cuts formed in the jacket of the treatment element.Altogether, a pumping action is produced, which makes liquid flow pastthe sharp edges.

Preferably, the treatment element is fitted on a stirrer or mixer havingseveral radially outwardly directed vanes. Preferably, the treatmentelement is mounted on the tips of the vanes, whereby the treatmentelement will form a cylindrically shaped enclosure around thestirrer/mixer. The vanes generate a rotary motion of the liquid inconsequence whereof the centripetal force will transport liquid andparticles radially outwards, away from the hub of the stirrer/mixer. Theflow through the cuts, and thus the flow past the sharp edges, thereforewill be larger.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following withreference to the accompanying drawings, wherein

FIG. 1 is a view from above of a presently preferred embodiment of thedevice in accordance with the invention,

FIG. 2 is an enlarged view of the area marked II in FIG. 1,

FIG. 3 is a lateral view of the device of FIG. 1, mounted on an electricmotor,

FIG. 4 is an enlarged view of the area marked IV in FIG. 3, and

FIG. 5 is a longitudinal sectional view through a vessel fitted with adevice according to FIG. 3 and located at the vessel bottom.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 5 illustrates a vessel intended for mixing liquids, preferably atank 1 made from sheet metal or plastic, preferably stainless steel orthe like. The tank 1 is formed with a circular opening 2, in which ismounted a circular disk 3 having a male coupling 4, which projects intothe tank interior. A flange 5 is attached, preferably by means ofwelding, to the rim of the opening 2 so as to extend peripherally aroundthe disk.

Furthermore, the disk 3 is attached, for examples by means of screws, toa preferably electric motor 6, the shaft of which extends from the outerface of the tank 1 and is connected to a male coupling 4. Inside thetank, a stirrer 7 is rotationally mounted on the male coupling 4, saidstirrer arranged to receive moment of force from the motor 6 by way of amagnetic drive of known configuration.

The motor 6 need not be electrically driven but alternatively could bee.g. pneumatically or hydraulically driven. In addition, the motor 6 maydrive the stirrer 7 directly, i.e. not via a magnetic drive, andfurthermore a gearbox may be inserted between the motor and the stirrerin order to provide the desired gear ratio between the rotational speedsof the stirrer and the motor, respectively. Instead of the motor 6 beingpositioned as illustrated it may be spaced from the tank 1 and drive thestirrer 7 for example by a belt-drive arrangement or some similar typeof force transmission.

The stirrer 7 is formed with radially outwardly projecting vanes 8,which are mounted at a slight angle axially. On the ends 9 of the vanes,a treatment element 10 in accordance with the present invention isattached, preferably by means of welding.

In accordance with the preferred embodiment, the treatment element 10 isconfigured as a cylindrical ring 1, which preferably is made from thinsheet metal, preferably stainless steel of the like. The jacket 15 ofthe cylinder 10 is formed with a number of through-holes 11 having sharpedges 12. In accordance with the preferred embodiment, the holes 11 arearranged in axially extending rows alternatingly comprising five andfour holes.

The cylinder 10 may be produced for example by punching the holes 11from a sheet-metal strip, the long sides of which are thereafter bentinto an annular shape. Therefore, the joint formed along the contactingshort sides of the bent strip can be welded together.

The holes could also consist of the meshes in a net produced byexpanding a material, in which through-slits have been made, which afterthe expansion form the sharp edges.

On the inner face of the cylinder 10, at each hole 11, shovels 13,having sharp edges 14, are formed.

Preferably, these shovels 13 are formed in conjunction with the punchingof the holes 11.

When the motor 6 drives the stirrer 7, as mentioned previously bymagnetic drive or the like, the cylinder 10 is being rotated about itscentre axis. This draws the shovels 13 through the liquid, the shovelmouths being orientated in the direction of rotation A, and the sharpshovel edges 14 transfer part of the moment of force of the stirrer 7 tothe liquid in the form of a shearing force. The shovels 13 transport theliquid further, from the inner face of the cylinder 10, through theholes 11 in the jacket 15 and to the exterior of the cylinder 10. Thesharp edges 12 of the holes 11 transfer shearing forces to the liquid inthe same manner as do the sharp edges 14 of the shovels 13.

The vanes 8 of the stirrer 7 set the liquid in a rotary motion, wherebythe liquid pressed outwards by the centripetal force, against the jacketof the cylinder. The rotary motion is strengthened at the inner face ofthe cylinder 10, where the shovels 13 contribute to setting the liquidin rotation.

In all, a pumping effect is created, causing liquid enclosed by therotating cylinder 10 to be kept rotating and consequently to be forcedby the centripetal force outwards, against the inner face of thecylinder 10. The shovels 13 contribute to this effect and then transportthe liquid from the inner face of the cylinder 10, through the holes 11,to the exterior of the cylinder 10. During this transport, the sharpedges 14 of the shovel mouths and the sharp hole edges 12 transfer partof the moment of force of the stirrer 7 to the liquid in the form ofshearing forces.

The shearing forces cause efficient mixing of liquids, also in the caseof dispersion or homogenisation of liquids that do not easily formsolutions, as also in the case of suspension of solids in liquid.

It will be appreciated that several modifications may be made to theembodiment described above within the scope of protection as defined inthe appended claims.

For example, the positions of the holes as well as their numbers couldbe varied. In addition, a shovel may be configured so as to extendacross several holes.

Furthermore, the cylinder may be shaped as a barrel or be formed withinwardly directed flanges at one or both ends, thus to counteract thetendency that liquid be forced to move axially along the jacket butinstead be made to pass through the holes.

The treatment element could also consist of several parts, such as anumber of concentric cylinders.

What is claimed is:
 1. A device for treatment of material in a vessel(1), particularly for dispersion or homogenisation of liquids, or forsuspension of solids in liquids, of the kind comprising a treatmentelement (10) that is rotationally mounted in the vessel (1),characterized in that the treatment element (10) essentially is oftubular configuration and is formed in a jacket (15) with a plurality ofcuts (11) formed with sharp edges (12), which are drawn through thematerial in the vessel as the treatment element rotates, in order totransfer shearing forces to said material wherein said treatment elementis enveloped by said material and at least one of the ends of thetreatment element (10) is formed with an inwardly directed flange.
 2. Adevice as claimed in claim 1, characterized in that the treatmentelement (10) has a barrel-shaped contour configuration.
 3. A device asclaimed in claim 1, characterized in that the cuts (11) are formed withshovel means (13), the mouths of which are orientated in the directionof rotation (A) of the treatment element, said mouths being formed withsharp edges (14).
 4. A device as claimed in claim 1, wherein thetreatment element (10) preferably is cylindrical and is mounted forrotation about its center axis.
 5. A device as claimed in claim 1,wherein the treatment element (10) is divided into at least two separatepieces.
 6. A device for treatment of material in a vessel (1),particularly for dispersion or homogenisation of liquids, or forsuspension of solids in liquids, of the kind comprising a treatmentelement (10) that is rotationally mounted in the vessel (1),characterized in that the treatment element (10) essentially is oftubular configuration and is formed in a jacket (15) with a plurality ofcuts (11) formed with sharp edges (12), which are drawn through thematerial in the vessel as the treatment element rotates, in order totransfer shearing forces to said material wherein said treatment elementis enveloped by said material and the treatment element (10) has abarrel-shaped contour configuration.
 7. A device as claimed in claim 6,characterised in that the cuts (11) are formed with shovel means (13),the mouths of which are oriented in the direction of rotation (A) of thetreatment element, said mouths being formed with sharp edges (14).
 8. Adevice as claimed in claim 6, wherein the treatment element (10)preferably is cylindrical and is mounted for rotation about its centeraxis.
 9. A device as claimed in claim 6, wherein the treatment element(10) is divided into at least two separate pieces.
 10. A device fortreatment of material in a vessel (1), particularly for dispersion orhomogenisation of liquids, or for suspension of solids in liquids, ofthe kind comprising a treatment element (10) that is rotationallymounted in the vessel (1), characterized in that the treatment element(10) essentially is of tubular configuration and is formed in a jacket(15) with a plurality of cuts (11) formed with sharp edges (12), whichare drawn through the material in the vessel as the treatment elementrotates, in order to transfer shearing forces to said material whereinsaid treatment element is enveloped by said material, wherein the cutsare the meshes of a net formed by expanding a material, in whichthrough-slits have been made, said slits forming said sharp edges.
 11. Adevice for treatment of material in a vessel (1), particularly fordispersion or homogenisation of liquids, or for suspension of solids inliquids, of the kind comprising a treatment element (10) that isrotationally mounted in the vessel (1), characterized in that thetreatment element (10) essentially is of tubular configuration and isformed in a jacket (15) with a plurality of cuts (11) formed with sharpedges (12), which are drawn through the material in the vessel as thetreatment element rotates, in order to transfer shearing forces to saidmaterial wherein said treatment element is enveloped by said materialand the treatment element (10) is fitted on a stirrer (7) having vanesthereon, said stirrer arranged to be driven via magnetic drive by adrive means (6) situated on the exterior of the vessel (1).
 12. A deviceas claimed in claim 11, characterised in that the vanes (8) of thestirrer (7) are directed radially outwardly, and in that the treatmentelement 10 is mounted on the outer ends (9) of these vanes (8).
 13. Adevice for treatment of material in a vessel (1), particularly fordispersion or homogenisation of liquids, or for suspension of solids andliquids, of the kind comprising a treatment element (10) that isrotationally mounted in the vessel (1), characterized in that thetreatment element (10) essentially is of tubular configuration and isformed in a jacket (15) with a plurality of cuts (11) formed with sharpedges (12), which are drawn through the material in the vessel as thetreatment element rotates, in order to transfer shearing forces to saidmaterial; wherein the cuts (11) are formed with shovel means (13), themouths of which are all orientated in the direction of rotation (A) ofthe treatment element, said mouths being formed with sharp edges (14).14. A device as claimed in claim 13, characterised in that the shovelmeans (13) are positioned on the inner face of the jacket (15).
 15. Adevice as claimed in claim 13, wherein the treatment element (10)preferably cylindrical and is mounted for rotation about its Centeraxis.
 16. A device as claimed in claim 13, wherein the treatment element(10) is divided into at least two separate pieces.
 17. A device fortreatment of material in a vessel (1), particularly for dispersion orhomogenisation of liquids, or for suspension of solids and liquids, ofthe kind comprising a treatment element (10) that is rotationallymounted in the vessel (1), characterized in that the treatment element(10) essentially is of tubular configuration and is formed in a jacket(15) with a plurality of cuts (11) formed with sharp edges (12), whichare drawn through the material in the vessel as the treatment elementrotates, in order to transfer shearing forces to said material; whereinthe treatment element (10) is cylindrical, is mounted for rotation aboutits center axis, is divided into at least two separate pieces, has abarrel-shaped contour configuration, is fitted on a stirrer (7) havingvanes thereon, said stirrer arranged to be driven via magnetic drive bydrive means (6) situated on the exterior of the vessel (1) wherein thevanes (8) of the stirrer (7) are directed radially outward, and thetreatment element is mounted on the outer end (9) of these vanes (8) andat least one of the end of the treatment element (10) is formed with aninwardly directing flange; and the cuts (11) are formed with shovelmeans (13), the mouths of which are orientated in the direction ofrotation (A) of the treatment element, said mouths being formed withsharp edges; and wherein the shovel means (13) are positioned on theinner face of the jacket (15).